Messages in this thread | | | From | Schspa Shi <> | Date | Sat, 9 Apr 2022 15:36:54 +0800 | Subject | Re: [PATCH] btrfs: zstd: use spin_lock in timer function |
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David Sterba <dsterba@suse.cz> writes:
> On Sat, Apr 09, 2022 at 02:15:23AM +0800, Schspa Shi wrote: >> timer callback was running on bh, and there is no need to disable bh again. > > Why do you think so? There was a specific fix fee13fe96529 ("btrfs: > correct zstd workspace manager lock to use spin_lock_bh()") that > actually added the _bh, so either you need to explain why exactly it's > not needed anymore and verify that the reported lockdep warning from the > fix does not happen.
Yes, I've seen this fix, and wsm.lru_list is protected by wsm.lock. This patch will not remove all changes that were fixed. Just a little improvement to remove the unnecessary bh disabling. Like static inline void red_adaptative_timer(struct timer_list *t) in net/sched/sch_red.c.
Because the critical section is only used by the process context and the softirq context, it is safe to remove bh_disable in the softirq context since it will not be preempted by the softirq.
BRs Schspa Shi
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